1. Field of the Invention
The present invention relates to a cuff apparatus for measuring the blood pressure, which has a cylindrical section containing an air bag (a bladder) and which is designed to suppress the flow of blood in a body part inserted in the cylindrical section. The invention relates also to a sphygmomanometer that comprises such a cuff apparatus.
2. Description of the Related Art
Cuff apparatuses for measuring blood pressures are known. They comprise a cylindrical section which incorporates an airbag (a bladder) and into which a body part (upper arm or forearm) is inserted so that the flow of blood in the body part may be suppressed. (Hereinafter, they shall be called “cuff apparatuses of body-part insertion type.”) As FIG. 12 shows (Unexamined Published Japanese Patent No. 10-314123), a cuff apparatus may comprise a cuff 100, an electric motor 200, and tapes 300. The motor 200 and the tapes 300 are used to pull and taken up the cuff 100.
The cuff apparatus, wherein the cuff is pulled and taken up, consumes much electric power, has a complex structure, is difficult to assemble, and is large and heavy.
The cuff may be shaped like a hollow cylinder and may incorporate an airbag (a bladder) that has a diameter much greater than the diameter of the body part (upper arm or forearm). Compressed air may be introduced into the airbag, reducing the inside diameter of the cuff until the cuff fits on the body part.
The cuff apparatus, in which the cuff fits on the body part as compressed air is introduced, is indeed smaller and lighter than the type in which the cuff is taken up. However, it is disadvantageous in the following respects.
First, the airbag needs to have a volume about four to five times as large as in the cuff of ordinary type, which is manually wrapped around the body part. It takes more time to introduce compressed air into the airbag. In view of this, four to five air-compressing pumps may be used. Alternatively, an air-compressing pump with an output capacity of four to five times as much may be employed. In either case, much power is consumed, and the cuff apparatus must comprise an AC power supply. Consequently, the sphygmomanometer becomes larger and heavier.
Second, the cylindrical airbag has a large inside diameter even before compressed air is supplied into it. The inside diameter of the cylindrical bag greatly changes (decreases) as air is forced into the airbag. Thus, the inner circumferential surface of the airbag (i.e., the surface contacting the body part) may have wrinkles by the time the bag fits on the body part, particularly at the part, which lies near the arteries existing in the body part. Wrinkles, if formed, may decrease the ability of suppressing the flow of blood. In a cuff apparatus for use in combination with a sphygmomanometer with which the sound of the bloodstream (i.e., Korotkoff sound) is detected to measure the blood pressure, the cuff needs to have a microphone for detecting the Korotkoff sound. The microphone may not contact the body part due to the wrinkles formed on the inner circumferential surface of the airbag. Consequently, the Korotkoff sound may not be detected correctly.
Third, the airbag, i.e., a cylindrical member secured to the inner circumferential surface of the hollow cylindrical chassis (case) into which the body part should be inserted, cannot sufficiently suppress the flow of blood at its ends. Hence, the airbag fails to suppress the flow of blood as is desired, if the chassis holds the body part, with the arteries located at the ends of the airbag.
Fourth, the cuff apparatus is difficult to assemble, because the airbag must be secured to the chassis with double-side adhesive tape or the like, while holding nozzles (conduits) at prescribed positions. Note that the nozzles are indispensable components for introducing and discharging compressed air into and from the airbag and detecting the pressure.
Fifth, the cloth cover provided on the inner circumferential surface of the airbag must be large enough so that the airbag may be fully inflated and have a small inside diameter (The cloth cover is so large while the inside diameter is so small.). Therefore, the cloth cover has wrinkles or slackens before the compressed air is supplied into the airbag.
Sixth, the cloth cover, which frequently contacts the body parts of subjects and likely gets dirty, should be replaced by a clean one after some use. However, the cover cannot be easily removed from, or attached to, the housing of the sphygmomanometer.
The present invention has been made in view of the problems with the conventional cuff apparatus of body-part insertion type, particularly the cuff apparatus in which the cuff fits on the body part as compressed air is introduced into it. An object of the invention is to provide a cuff apparatus in which compressed air can be introduced into the cuff within a short time and which is easy to handle and assemble. Another object of the invention is to provide a sphygmomanometer which comprises such a cuff apparatus, which is easy to handle and assemble and which is small and lightweight.